摘要:

Grain boundaries in GaP and InP have been studied by infrared cathodoluminescence (CL). In GaP the results indicate that there exists a depletion region beside grain boundaries where the concentration of PGaantisite defects is lower than in the bulk material. In InP the near‐edge CL emission and a deep level luminescence at 1.07 eV have been found to cause similar grain boundary CL contrast.

ISSN:0021-8979    

DOI:10.1063/1.347692

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The width of the spectral lines related to intraimpurity transitions in GaAs is determined by random electric fields of charged acceptors and donors. The broadening of spectral lines with the increase in temperature was interpreted as the transition from correlated distribution of electrons located on the donors to the random distribution. Baranovskii and Shklovskii [Sov. Phys. Semicond.23, 122 (1989)] suggested that the distribution function for intermediate temperatures may be approximated in a lightly doped weakly compensated semiconductor as joint probability distribution for two independent systems. In this paper, the dependence of the line width on temperature is obtained using their approach.

ISSN:0021-8979    

DOI:10.1063/1.347693

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Hydrogenated amorphous silicon (a‐Si:H) films have been fabricated by a plasma chemical vapor deposition (plasma‐CVD) method at low substrate temperatures (Ts: 80 or 50 °C) to obtain wide‐gap films. Device‐quality wide‐gap films (photoconductivity under AM‐1.5, 100 mW/cm2illumination ∼10−5&OHgr;−1 cm−1, ratio of photoconductivity and dark conductivity ∼106, and Tanc’s gap ∼2 eV) are obtained at lowTs, by optimizing the plasma parameters or by diluting the material gas (SiH4) with H2. Experimental results suggest that lowering the deposition rate ofa‐Si:H films is an important factor in obtaining high‐quality films at lowTsusing a plasma‐CVD method.

ISSN:0021-8979    

DOI:10.1063/1.347694

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Carbon‐doped GaAs films have been grown by solid‐source molecular beam epitaxy using a graphite filament. The films were doped from 1×1015cm−3to 5×1019cm−3and the resulting mobilities are equivalent to beryllium‐doped films. A slight dependence of As4/Ga flux ratio on carbon doping was observed. The use of either As2or As4did not significantly affect the carbon doping concentrations. Lattice contractions were observed for films doped heavily with carbon or beryllium. For a given doping concentration the contraction is more significant for carbon doping which is consistent with the smaller tetrahedral covalent radius of carbon compared to beryllium. Good agreement between observed and calculated lattice contractions with carbon doping is obtained. Annealing studies on a film doped with carbon at 5×1019cm−3indicate that the electrical properties and lattice contraction are quite stable.

ISSN:0021-8979    

DOI:10.1063/1.347695

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The epitaxial growth of terbium silicide by codeposition on Si(111) is demonstrated. Terbium and silicon are evaporated onto substrates held at room temperature and subsequently annealed up to 850 °C, where the pressure during evaporation and annealing is maintained below 1×10−9Torr. Low‐energy electron diffraction shows a sharp (3)1/2×(3)1/2pattern of the hexagonal silicide after an 850 °C anneal. The morphology in these films in much improved over that of metal reacted layers with pinholes of <0.15 &mgr;m in diameter. Rutherford backscattering analysis indicates single‐crystal growth with a channeling minimum yield of 9% for 150‐A˚‐thick silicide films annealed to 800–850 °C. Plan view electron microscopy shows the evidence of faults along ⟨2¯20⟩ directions, but no indication of a superstructure in the silicide layer. The microstructure of the thick film is shown to be strongly affected by the formation of a template layer prior to thick film deposition.

ISSN:0021-8979    

DOI:10.1063/1.347696

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Extremely narrow photoluminescence linewidths have been observed from 6‐A˚ quantum wells of GaAs/In0.11Ga0.89As/GaAs. The quality of these spectra is such that structure involving higher‐order donor‐exciton transitions are observed.

ISSN:0021-8979    

DOI:10.1063/1.347697

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Knowledge of both carrier bulk lifetime &tgr;band surface recombination velocitySare necessary to analyze and model electron devices. In this paper, the analytical results of Luke and Cheng [J. Appl. Phys.61, 2282 (1987)] are applied to examine excess carrier decay due to pulsed Gaussian optical excitation to extract values of &tgr;bandSunder low level injection. The nondestructive, contactless measurement technique utilizes a visible pulsed laser pump beam and a CW infrared laser probe beam. Values for &tgr;bandSare obtained for a number of different Si samples. The effect of varying the pump beam frequency is examined. The technique is simple to use in the laboratory and the parameter extraction from the measured data is straightforward.

ISSN:0021-8979    

DOI:10.1063/1.348933

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A new method to prepare nanocrystalline alloys was developed by means of crystallization from amorphous alloys. By using this method, a Ni‐P alloy with 9 nm crystallites was synthesized. The structures and grain sizes of the alloy were examined by means of x‐ray diffraction, transmission electron microscopy, and high resolution electron microscopy. Specific heat capacity and thermal expansion coefficient of the nanocrystalline Ni‐P alloy prepared by this method were found to be greater than those of the coarse‐grained crystalline alloy by 12.3% and 56.2%, respectively. A new micromechanism for nanometer‐sized crystallites formation is discussed.

ISSN:0021-8979    

DOI:10.1063/1.347698

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Longitudinal uniaxial stress along ⟨100⟩ has been applied in AlAs‐GaAs‐AlAs resonant tunneling heterostructures grown on (100) substrates to study the current‐voltage characteristics as a function of stress. We find that the nonresonant current is due to Fowler–Nordheim tunneling currents by both longitudinal and transverseXvalleys (X1andXt). This current decreases with low stress (<1 kbar), increases with intermediate stress and decreases with high stress (>9 kbar) again. This is due to the increase of theXtbarrier at low stress, the decrease of theX1barrier at intermediate stress, and the formation and the increase ofX1potential well depth at high stress. We also find a large unexplained monotonic decrease of the resonant current through the &Ggr; valley.

ISSN:0021-8979    

DOI:10.1063/1.347699

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The subthreshold characteristics ofn‐channel metal‐oxide‐semiconductor field effect transistors after high‐field, high current density (100 mA/cm2) Fowler–Nordheim electron injection are investigated. Rapid changes are observed and recorded within 1000 s after injection. A ‘‘bump’’ in the subthresholdI‐Vcharacteristic appears if electron trapping in the gate oxide dominates. This bump can be made to disappear and reappear by controlling the amount of trapped electrons in the oxide. This may be readily explained by the parasitic channel leakage current along the isolation field oxide edges.

ISSN:0021-8979    

DOI:10.1063/1.347700

出版商:AIP    

年代:1991

数据来源: AIP